It is often convenient to save a notebook to its present folder under a new name. This requires the use of SaveAs. Similarly, some notebooks such as style sheets need to be saved using SaveAs even when retaining their present name. The most convenient thing for the system to do is to bring up the notebook's existing folder as the start point for any folder browsing .
In earlier versions of Mathematica this worked properly, then in Version 8 (I think) this got broken and in Version 9 (or 9.01) it got fixed. Now in Version 10 it is again broken. Instead it brings up the last directory used, with no relation to the present notebook.
Similarly, the word completion feature in Text cells has slowly slipped away. In Version 9 it worked but always gave a spurious error message. I sent numerous messages to WRI on this through their automatic error reporting form. Now in Version 10 word completion doesn't work at all. This was a very useful feature for checking spelling on single words. (It would also be quite nice if one could spell check a single Text cell.)
It is quite disconcerting that standard useful features, that were working and that one might hope were stable, slip away in newer versions. And that these aren't even caught in beta testing.
Could we expect these to be fixed in a Version 10 update?